In 1850, a presidential order set aside the island for possible use as a United States military reservation. The California Gold Rush, the resulting boom in the growth of San Francisco, and the need to protect San Francisco Bay led the U.S. Army to build a Citadel at the top of the island in the early 1850s. The Army also made plans to install more than 100 cannons on the island, making Alcatraz the most heavily fortified military site on the West Coast. The island was also the site of the first operational lighthouse on the West Coast of the United States. By the late 1850s, the first military prisoners were being housed on the island. In 1909, the Army tore down the Citadel, leaving its basement level to serve as the foundation for a new military prison. From 1909 through 1911, the military prisoners on Alcatraz built the new prison, which was designated the Pacific Branch, U.S. Disciplinary Barracks for the U.S. Army. It was this prison building that later became famous as "The Rock." The U.S. Army used the island for more than 80 years-from 1850 until 1933, when the island was transferred to the U.S. Department of Justice for use by the Federal Bureau of Prisons. The Federal Government had decided to open a maximum-security, minimum-privilege penitentiary to deal with the worst inmates in Federal prisons, and to show the law-abiding public that the Federal Government was serious about stopping crimes of the 1920s and 1930s.